1. Field of the Invention
The present invention relates to a temperature controlling method, a thermal treating apparatus for a semiconductor manufacturing device or the like, and a method for manufacturing a semiconductor device, and in particular, it relates to a temperature controlling method and a thermal treating apparatus for a semiconductor device or the like, and a method for manufacturing a semiconductor device, wherein in order to thermally treat a treatment target, the thermal treating apparatus is divided into a plurality of heating zones, and target temperatures are set for the plurality of heating zones for temperature control so that the target temperatures are corrected using temperatures detected in areas of the treatment target the number of which is larger than the number of the plurality of heating zones.
2. Description of the Related Art
With known thermal treating apparatuses, if, a semiconductor wafer (substrate) as a treatment target is thermally treated for film formation or the like, various temperatures are required which correspond to the types of films formed as a result of the treatment and a fabrication process thereof. Accordingly, during the thermal treatment, the temperature of the treatment target is controlled so as to be as close to the treatment temperature as possible (soaking control method). FIG. 6 is a diagram showing the structure of a vertical diffusion furnace, which is typical of such thermal treatment apparatuses. The vertical diffusion furnace shown in FIG. 6 is composed of a soaking pipe 112 and a reaction pipe 113 covered by an outer wall 111, a heater 114 for heating the inside of the reaction pipe 113, heater thermocouples 115 for detecting the temperatures of the heater 114 at a plurality of locations thereof, cascade thermocouples 116 for detecting the temperature at locations between the soaking pipe 112 and the reaction pipe 113, a boat 117 on which a wafer to be subjected to thermal treatment is mounted, and a temperature controller 119 for controlling the amount of operation Z (value of electric power) for the heater 114 on the basis of the temperatures detected by the heater thermocouple 115 and the cascade thermocouple 116 as well as an indicated target temperature Y.
The heater 114 is divided into a plurality of heating zones so as to accurately control the in-furnace temperature (temperature of the reaction pipe 113). If the heater 114 is divided, for example, into four heating zones as shown in FIG. 6, the zones are called U, CU, CL, and L zones (hereinafter these names will be used) respectively from the top to the bottom of the figure. Each of the heating zones has the heater thermocouples 115 and the cascade thermocouples 116 installed therein. In order that the temperatures detected by the cascade thermocouples 116 equal the target temperature, the temperature controller 119 detects the temperatures of the heater thermocouples 115 while calculating the amount of operation Z for the heater 114 in accordance with a given algorithm (PID calculations or the like), thereby adjusting the power value for the heater 114.
In this manner, the conventional temperature control is executed so that the temperatures detected by the cascade thermocouples 116 equal the target value for the wafer treatment. Accordingly, there may be not a small difference between the temperature at the location of the wafer to be actually treated and the corresponding temperature detected by the cascade thermocouple, thereby degrading the quality of the thermal treatment. Thus, it is necessary to control the temperature of an area closer to the wafer or the temperature of the wafer itself so as to equal the target value for the wafer treatment in order to improve the quality of the thermal treatment. To achieve this, a means is required which detects the temperature of an area closer to the wafer or the temperature of the wafer itself. The detection means includes various methods such as the one of inserting thermocouples into the reaction tube to measure the temperatures of the neighborhoods of the wafer, or estimating the wafer temperatures using a mathematical model. Here, by way of example, a description will be given of a method of using temperature measuring wafers (thermocouple-mounted wafers) each comprising a thermocouple directly installed on a wafer.
FIG. 7 shows an example using the above described thermocouple-mounted wafers. In this case, thermocouple-mounted wafers 118 are arranged so as to correspond to the U, CU, CL, and L zones, the four heating zones. The heater thermocouples 115 and the cascade thermocouples 116 are also installed at locations corresponding to the U, CU, CL, and L zones. The temperatures detected by the thermocouple-mounted wafers 118 are obtained not only by the heater thermocouples 115 and the cascade thermocouples 116 but also by the temperature controller 119. Further, for the thermocouple-mounted wafers, the location at which the thermocouple is installed and the number of thermocouples installed may depend on the usage thereof. For the thermocouple-mounted wafers 118 in the example described herein, it is assumed that only one thermocouple is installed in the center of the wafer.
FIG. 9 shows an example of the relationship between the temperatures detected by the cascade thermocouples 116 and the thermocouple-mounted wafers 118, wherein the temperature control is executed so that the temperatures detected by the cascade thermocouples 116 equal the target value for the wafer treatment. In this case, the temperatures (◯) detected by the cascade thermocouples 116 equal the target value, whereas there may be errors between the temperatures (xcex94) detected by the thermocouple-mounted wafers 118 and the target value. Further, since the magnitude of the error and the like varies among the heating zones, this constitutes a factor reducing the quality of the thermal treatment. In this case, the errors between the temperatures detected by the thermocouple-mounted wafers 118 and the target temperature for the cascade thermocouples 116 may be used as corrective values for this target temperature. For example, in FIG. 9, if the temperature detected by the thermocouple-mounted wafer for the U zone is lower than the target value by 5xc2x0 C., then this 5xc2x0 C. can be used as a corrective value for the target temperature for the corresponding cascade thermocouple.
The above described correction increases the temperature detected by the cascade thermocouple 116 for the U zone, above the original target value by 5xc2x0 C., but the temperature detected by the thermocouple-mounted wafer for the U zone can be made equal to the original target value. FIG. 10 shows an example of the relationship between the temperatures detected by the cascade thermocouples and the thermocouple-mounted wafers, wherein the correction is executed for all the heating zones. In this case, the temperatures (◯) detected by the cascade thermocouples 116 do not equal the original target value, whereas the temperatures (xcex94) detected by the thermocouple-mounted wafers 118 equal the target value. The temperature of wafers to be actually thermally treated equals the target value, so that the quality of the thermal treatment can be improved. In this example, however, even if 5xc2x0 C. is added to the target value for the cascade thermocouple as a corrective value in order to increase the temperature detected by the thermocouple-mounted wafer 118 by 5xc2x0 C., the temperature detected by the thermocouple-mounted wafer often fails to actually increase by 5xc2x0 C., thereby requiring an adjustment operation to be repeated several times.
Furthermore, in the construction shown in FIG. 7, the thermocouple-mounted wafers 118 are arranged at the locations corresponding to the heater thermocouples 115 and cascade thermocouples 116 installed for the respective heating zones. In contrast, FIG. 11 shows an example of the relationship between the temperatures detected by the cascade thermocouples and the thermocouple-mounted wafers, wherein in order to measure the temperatures of other wafers, additional plural thermocouple-mounted wafers are arranged as shown in FIG. 8 and temperatures detected thereby are similarly obtained by the temperature controller 119. In this case, the temperatures (xcex94) detected by the thermocouple-mounted wafers 118 arranged at locations representative of the corresponding heating zones equal the target value, whereas the temperatures (▴) detected by the thermocouple-mounted wafers arranged at locations different from those mentioned above have errors with respect to the target value. This may lead to differences in the quality of the thermal treatment, thus reducing the rate at which products having a quality of a fixed level are manufactured. To prevent this, the target temperature for the cascade thermocouples 116 may further be corrected so as to minimize the differences in temperature between the wafer areas to thereby obtain a uniform temperature.
For example, if the temperature detected by the thermocouple-mounted wafer installed between the CL zone and the L zone is 3xc2x0 C. higher than the target value, the target temperature for the cascade thermocouple for the CL and L zones are reduced by about 1xc2x0 C. as a corrective value. In this case, the corrective value is set at 1xc2x0 C. instead of 3xc2x0 C. because if the error of 3xc2x0 C. is used as a corrective value for the target temperature for the cascade thermocouple as described above, then with respect to the temperatures detected by the thermocouple-mounted wafers corresponding to the heating zones the error is too large compared to the target temperature, thereby preventing the attainment of the object to eliminate the difference in temperature between the wafer areas. Another explanation for the setting of the corrective value at 1xc2x0 C. is as follows. The temperature detected by the thermocouple-mounted wafer installed between the CL zone and the L zone is affected by corrections for the CL and L zones. Accordingly, if information such as the level of the interference between the heating zones is insufficient, the corrective value must be adjusted a number of times. Thus, the initial value is set at almost 1xc2x0 C.
FIG. 12 shows an example of the relationship between the temperatures detected by the cascade thermocouples and the thermocouple-mounted wafers, wherein with the construction as shown in FIG. 8, the temperatures detected by all the thermocouple-mounted wafers are adjusted (for example, by a skilled operator) so as to reduce the errors with respect to the target value. In this case, the temperatures (xcex94) detected by the thermocouple-mounted wafers corresponding to the heating zones slightly deviates from the target value, but for all the thermocouple-mounted wafers (xcex94, ▴), the errors in the detected temperatures with respect to the target value are generally smaller than in FIG. 11 (the width of the variation shown by the arrow is smaller). This serves to increase the number of products having a quality of a fixed level or higher. A skilled operator, however, is required in reducing the errors in the thermocouple-mounted wafers with respect to the target temperature as shown in FIG. 12. Further, it presently takes even skilled operators much time to adjust the errors because the adjustment operation must be repeated many times.
The above described conventional soaking control method for thermal treatment apparatuses comprises dividing the wafer areas of the thermal treatment apparatus into a plurality of heating zones, actually setting target temperatures for all the heating zones, detecting the temperatures of areas subjected to temperature using temperature detecting devices such as the cascade thermocouples in peripheries of the furnace, and providing heating control using the detected temperatures so that treatment targets arranged in the furnace can be treated at the target temperature. Since, however, the determination of a set temperature for the temperature detecting devices depends on the skilled operator""s experience or trials, the number of proper able personnel is limited and much time is required for the setting.
The present invention is intended to obviate the above problems, and has for its object to provide a temperature control method, a thermal treatment apparatus, and a method of manufacturing a semiconductor device, which can simply and promptly adjust (soaking control) the temperatures of all areas of a treatment target to a target value while reducing resulting errors and which can be easily automated using a computer system.
Bearing the above object in mind, according to a first aspect of the present invention, there is provided a temperature control method of controlling a heating apparatus having at least two heating zones so as to adjust temperatures detected at predetermined locations to a target value therefor, the method comprising: detecting temperatures at the predetermined locations the number of which is larger than the number of the heating zones and at least one of which is in each of the heating zones; and controlling the heating apparatus in such a manner that the target temperature falls between a maximum value and a minimum value of a plurality of temperatures detected at a plurality of detected predetermined locations.
With this configuration, even without any skilled operator, the temperatures of all areas of a treatment target can be simply and promptly adjusted (soaking control) to a target value while reducing resulting errors. Thus, the present invention is easily applicable to a vertical CVD apparatus or a sheet-feed apparatus which has a plurality of heating zones and which allows the detection of temperatures at the locations of thermocouple-mounted wafers.
In a preferred form of the first aspect of the present invention, first temperature detectors are disposed at first predetermined locations corresponding to the respective zones, and are used for a temperature control method of controlling the heating apparatus in such a manner that temperatures detected by the first temperature detectors equal a first target temperature. Second temperature detectors are disposed at second predetermined locations which are closer to a treatment target than the first predetermined locations, to obtain an interference matrix M as well as differences P0 between a second target temperature for the second temperature detectors and temperatures detected by the second temperature detectors, the interference matrix M being a matrix of coefficients indicative of the extents of variations of temperatures detected by the second temperature detectors when the first target temperature for the first temperature detectors is varied. The first target temperature is corrected on the basis of the interference matrix M and the errors P0.
With the this configuration, even if there is not any skilled operator, the temperatures of all areas of the treatment target can be simply and promptly adjusted (soaking control) to a target value while reducing resulting errors, and the system can be automated using a computer system. Here, note that in an embodiment of the invention, the first temperature detectors correspond to cascade thermocouples, and the second temperature detectors correspond to thermocouples attached to wafers (thermocouple-mounted wafers). With this construction, temperature control can be carried out while correcting the target temperature for the cascade thermocouples on the basis of the interference matrix M and the errors P0 obtained.
In another preferred form of the first aspect of the present invention, the temperature control method further comprises: determining new errors P0xe2x80x2 by performing temperature control using the corrected first target temperature; and correcting the corrected first target temperature using the new errors P0xe2x80x2 and the interference matrix M.
With this configuration, the temperature control can be accurately carried out to precisely heat the treatment target at a desired temperature.
According to a second aspect of the present invention, there is provided a temperature control method for controlling an apparatus which includes a process chamber, a heating apparatus having at least one heating zone for heating a treatment target provided in the process chamber, and first temperature detectors provided at least one for each zone for detecting heating temperatures provided by the heating apparatus at first predetermined locations, wherein the heating apparatus is controlled on the basis of first detected temperatures detected by the first temperature detectors and a first target temperature for the first detected temperatures, and wherein a plurality of second temperature detectors are disposed at second predetermined locations the number of which is larger than that of the heating zones and which are closer to the treatment target than the first predetermined locations, the second temperature detectors being operable to detect heating temperatures provided by the heating apparatus. The method comprises: comparing second detected temperatures detected by the second temperature detectors with a second target temperature for the second detected temperatures to obtain corrective values for the first target temperature; and correcting the first target temperature by the corrective values to perform temperature control.
In a preferred form of the second aspect of the present invention, the corrective values are obtained before an actual process of actually treating a substrate to be treated.
With the above configurations of the second aspect of the invention, no second temperature detector needs to be provided in the actual process, thereby preventing the adverse effects of the provision of the temperature detectors on the treatment target.
According to a third aspect of the present invention, there is provided a thermal treatment apparatus comprising: a process chamber; a heating apparatus having at least two heating zones and being subjected to temperature control in such a manner that temperatures detected at predetermined locations equal a target temperature therefor; a plurality of temperature detectors for detecting temperatures at predetermined locations the number of which is larger than the number of the heating zones and at least one of which is in each of the heating zones; and a control device for controlling the heating apparatus in such a manner that the target temperature falls between a maximum value and a minimum value of a plurality of temperatures detected by means of the plurality of temperature detectors.
With this configuration, a thermal treatment apparatus can be provided with which even without any skilled operator, the temperatures of all areas of a treatment target can be simply and promptly adjusted (soaking control) to a target value while reducing resulting errors.
According to a fourth aspect of the present invention, there is provided a method of manufacturing a semiconductor device, in which a target substrate is subjected to a heating process by controlling a heating apparatus having at least two heating zones in such a manner that temperatures detected at predetermined locations equal a target temperature therefor, the method comprising: detecting temperatures at predetermined locations the number of which is larger than the number of the heating zones and at least one of which is in each of the heating zones; and controlling the heating apparatus in such a manner that the target temperature falls between a maximum value and a minimum value of a plurality of temperatures detected at a plurality of detected predetermined locations.
With this configuration, a method of manufacturing a semiconductor device can be provided with which even without any skilled operator, the temperatures of all areas of a treatment target can be simply and promptly adjusted (soaking control) to a target value while reducing resulting errors.